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Duration
The length of time an insulin remains active in the system. Since activity decays on a half-life curve, there is no actual hard time when duration has ended -- it's a matter of degree. The usual time used for reference is either whatever the manufacturer claims, or the time when blood glucose levels have reached the same point they were at shot time. Any residual effect of the insulin beyond that time is carryover. Duration is also quite individual--can vary from patient to patient and even with the same patient. The insulin time activity profiles you see are basically averages of blood glucose levels in a test group or groups of patients for a given time period. Some tested patients experienced longer than average duration, while for others it was less than average. Many of the duration test results done by manufacturers of human approved insulins are based on two patient groups--those with diabetes and non-diabetics who agreed to assist in the study. This combined and averaged data is used to generate the time activity profile. It means that there are VERY few with diabetes whose personal insulin activity profile is a perfect replica of those displayed. It follows then, that onset and peak times found on insulin time activity profiles are just as subject to variability as is duration, since they are all obtained in the manner above. Duration varies by species and strength, in addition to type. With regard to cats and dogs, the closest or perfect amino acid matches to their own native insulin (cats=beef) (dogs=pork) means faster onset, peak and shorter duration. For both, use of r-DNA/GE/GM insulins would mean a slower onset, peak and a longer duration, due to these differences. It's just the reverse for people, with the r-DNA/GE/GM insulins acting and peaking faster and having less duration than either beef or pork insulin products. Comparing similar insulins with only strength differences means that the U100 strength insulin will have a slower onset, peak and longer duration than an insulin which is U40, U50 or even U80, which is available in some countries. An example of comparison for strength would be the 3 versions of 100% bovine PZI insulin available. Hypurin Bovine Protamine Zinc and Insuvet Protamine Zinc are both U100 insulins. BCP also produces a U100 version of its 100% beef PZI. All three would have the same length of duration. Switching strengths, however, changes things. Having BCP PZI in either U40 or U50 strength, as opposed to the BCP U100 PZI, Hypurin and Insuvet, means that the U40 and U50 strengths of the PZI BCP makes will have a faster onset, peak and less duration than the 3 U100 100% beef PZI insulins. The type of insulin is the same-PZI, the species is the same-beef. The less strength an insulin has, the better it is absorbed. Better or faster absorption means a faster onset and peak but shorter duration. Using a less than U100 strength insulin is on the same principle as rapid-acting analog insulins. The analog insulins have their amino acid sequences altered to produce a faster onset and peak with shorter duration. Diluting insulin from U100 strength does the same thing without altering the molecule. Knowing this, particularly in the case of cats, who are the primary users of PZI insulins, means that you can switch from a U40 or U50 insulin strength to U100 if duration is a problem and conversely, away from U100 to U40 or U50 if less duration or faster onset is needed--all without leaving bovine PZI. See also peak, onset, carryover and Insulin. Category:TermsCategory:TipsCategory:TreatmentsCategory:InsulinsCategory:Regulation